Ryan Reynolds chose not to become close with his "movie" children. He wasn't mean or rude to them, just very distant. So distant in fact that the children often confided to those on the set that "Ryan doesn't like us!" Ryan said that he didn't want to "fall in love" with the kids. Ryan did this so that when "George Lutz" started changing, he'd have no trouble easing into the verbal and physical abuse.

For the closet scene with the babysitter, the production crew had originally ordered in a rubber door. After shooting the scene a few times, they decided it didn't look right, and they ultimately decided on using a real wooden door, so actress Rachel Nichols had to bang her hands on the door for two days straight while filming the scene.

In the original script, the poster on Billy's bedroom wall during the babysitter scene was of a different band. However, when the crew realized how long of a tongue actress Rachel Nichols (who played the babysitter) had, they decided to change it to a poster of the rock band KISS, because of band member Gene Simmons' very long tongue.

Except for the attic windows and the vaguely Dutch Colonial style, the reproduction of the house does not resemble the actual house in Amityville as it was at the time the events were said to have taken place. Also, because of huge tourist interest in the house, the original house has been altered and is now less recognizable.

This was the last picture Metro-Goldwyn-Mayer (MGM) released as an independent company. On 8 April 2005, the studio was acquired by several companies, including Sony, in the middle of the promotion for this movie. Several other films, including Into the Blue (2005) and The Pink Panther (2006), were already produced and set for release by MGM at the time of the buyout, and were later released by Sony Pictures.

While the reproduction of the Amityville House's famous exterior was constructed in Silver Lake, Wisconsin, many of the interiors were built on a temporary sound stage in an empty building located in a corporate park in Buffalo Grove, Illinois. The production company took out building permits in the village of Silver Lake, Wisconsin (in Kenosha County) and spent about $60,000 to adapt the historic Rustman House summer estate on the south shore of Silver Lake at Kenosha County Highways F and SA for its cinematic debut. (The Rustman fortune was earned in the Jefferson Ice company of Chicago in the harvesting and storage of ice from the wintertime lakes of Kenosha County and elsewhere, and shipping it to hotels for summertime usage and cooling before the advent of refrigeration.) The Rustman Estate consists of the "big" house. a smaller guest cottage, several farm buildings, two workers' cottages, a boathouse, a one-lane bowling alley, and wide pastures, garden plots and wooded areas. The porch on the house itself faces west and winds three-quarters of the way around the first floor. Inside there is a smallish kitchen but a dining room that seats 18-20 guests, a large living room, billiard room, butler's pantry, billiard room, and separate two-room maid's quarters. On the grand staircase was a stained-glass window (now removed) featuring an Eve-like maiden offering the viewer and apple. Upstairs, a vast master suite has been created from some of the original five upstairs bedrooms, each with its own marble sink. The third floor is the attic with a turret room high above Silver Lake where Mrs. Rustman would sit and watch the ice-cutters. The Rustman House awaits its next occupants as it has been unoccupied for several years and remains protected by a chain-link fence and hidden security devices.

In the Bio program Celebrity Ghost Stories, Melissa George confirmed the super natural feelings she had on the set when the cameras weren't rolling. Also during production, she along with the rest of the cast and crew learned that the real Kathy Lutz, whose story inspired the movie, had sadly passed away before shooting was finished.